Reflector with metallic matrix composite support and method of manufacturing it

ABSTRACT

To manufacture a reflector formed by a reflective metallic layer on a metallic matrix composite support, a metallic layer having a reflective surface whose shape is at least approximately identical to the required geometrical shape is disposed on a mold surface having a geometrical shape complementary to the required geometrical shape of the reflector. Fibers to constitute the composite support are draped on the metallic layer. They are metallized by the metallic or intermetallic material to form the metallic matrix. This layer and the metallized fibers are subjected to temperature and pressure conditions adapted to press the reflective surface strongly against the mold surface and to cause diffusion welding of the layer with the metallized fibers and of the metallized fibers with themselves so as to integrate the layer to the composite support during consolidation of the latter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns the manufacture of a reflector having a metallicreflective surface adapted to reflect luminous radiation (in which casethe expression "optical mirrors" is commonly used) or non-opticalradiation (infrared, etc.) and a metallic matrix composite supportextending along the surface.

2. Description of the Prior Art

The use of metallic matrix composite materials for dimensionally stablestructures such as optical supports, for example, is well known. Thesematerials have advantages including the following:

the materials are sealed, so that there is no absorption or desorptionof moisture, which is beneficial in applications such as spaceapplications where desorption could cause unwanted deformations (or evenpollution of sensors); and

the materials are thermally conductive, in particular in the directionof their thickness, which greatly facilitates achieving thermalequilibrium of the structure.

These two properties, combined with the fact that the mechanicalperformance (stiffness and strength) and the coefficients of thermalexpansion are beneficial, mean that metallic matrix composites(especially those using light alloys such as aluminum, aluminum alloys,magnesium and magnesium alloys, or copper and copper alloys, which areadvantageous because of their thermal conductivity and their ability towithstand high temperatures), and intermetallic matrix composites(including titanium aluminide and nickel aluminide which areadvantageous because of their high temperature resistance) areparticularly suitable for use in all structures requiring highdimensional stability, such as space telescopes or terrestrialtelescopes, for example.

The reflective surface, whether metallic or otherwise, is conventionallyfitted to its support by gluing it or by electrolytic depositionsubsequent to fabrication of the support, for example.

See for example the article by SULTANA and FORMAN of MIT, Lincoln Lab.,Lexington, Mass., USA, entitled "Dimensional stability concerns in themanufacture of graphite/epoxy beam steering mirrors", published inProceedings of SPIE--The International Society for Optical Engineering,Conference held at San Diego, Calif., USA, 12-13 Jul. 1990--whichproposes a laser cavity mirror for space radar including agraphite/epoxy matrix to which an aluminum coating is glued at ambienttemperature using an epoxy adhesive.

See also the article by WENDT and MISRA, of MARTIN-MARIETTA ASTRONAUTICSGROUP, DENVER, Colo., USA, entitled "Fabrication of near-net shapegraphite-magnesium composite for large mirrors" published in Advances inoptical structure systems; Proceedings of the Meeting, Orlando, Fla.,Apr. 16-19, 1990 (A91-36651 15-74), Ballingham, Wash., Society ofPhoto-Optical Instrumentation Engineers, 1990, pp 554-561, whichconcerns the fabrication of large stable mirrors for space surveillancesystems and laser systems including a carbon/magnesium composite supportonto which a 127 μm copper layer is deposited.

The disadvantages of attaching the reflective surface to a supportalready formed include:

the interface between the support and the reflective surface constitutesa discontinuity in the direction of the thickness of the reflector whichcan lead to at least localized separation in the event of thermalcycling, for example, or which can degrade the dimensional stability ofthe support (absorption-desorption in the case of a glue, play in thecase of mechanical couplings, etc.);

the geometry of the reflective surface is determined by the geometry ofthe support and the quality of the process used for attaching thereflective surface, which almost always requires subsequent machining ofthe surface to meet the shape requirement; and

the mass and the cost of the reflector are higher.

An object of the invention is to alleviate the above drawbacks.

The basic idea of the invention is to determine the geometry of theactive surface (free surface) of the reflective surface directly and toensure the greatest possible continuity within the thickness of thereflector between the reflective surface and its support.

SUMMARY OF THE INVENTION

The invention resides in a method of manufacturing a reflector formed bya reflective metallic layer on a metallic matrix composite support,wherein:

a metallic layer having a reflective surface whose shape is at leastapproximately identical to the required geometrical shape is disposed ona mold surface having a geometrical shape complementary to the requiredgeometrical shape of the reflector;

fibers adapted to constitute the composite support are draped on themetallic layer, the fibers being metallized by the metallic orintermetallic material adapted to form the metallic matrix; and

the layer and the metallized fibers are subjected to temperature andpressure conditions adapted to press the reflective surface stronglyagainst the mold surface and to cause diffusion welding of the layerwith the metallized fibers and of the metallized fibers with themselvesso as to integrate the layer to the composite support duringconsolidation of the support.

According to preferred features of the invention, some of which may becombinable with others:

the fibers are carbon or graphite fibers;

the fibers are disposed symmetrically on either side of a median surfaceof symmetry;

the fibers are draped onto the metallic layer in the free state relativeto each other;

the fibers are divided into an even number of layers disposedsymmetrically to either side of a median surface of symmetry;

the metallized fibers are prepared by vapor phase physical deposition ofa layer of metallization onto the fibers so that the metallized fibersare flexible;

the fibers are stranded, rather than free;

the stranded metallized fibers are metallized by dipping into a bath ofmolten metallic material or by infiltration;

in an alternative embodiment, the fibers are grouped in plates in whichthe fibers have one, two or three alignment directions;

the plates of metallized fibers having one, two or three alignmentdirections are obtained by infiltration of the metallic material in themolten state under pressure;

the metallic or intermetallic metallization material is selected fromthe group of aluminum, aluminum alloy, magnesium, magnesium alloy,copper, copper alloy, titanium, titanium alloy and aluminides, inparticular titanium aluminide and nickel aluminide;

the metallic layer is placed on the mold surface in the form of one ormore deformable films;

the metallic layer is obtained by preparation of a metallic blank havinga blank surface at least approximately identical to the requiredgeometrical shape, the blank being deformable under the temperature andpressure conditions at least in a part of its thickness underlying theblank surface,

the blank is deformable under the temperature and pressure conditionsthroughout its thickness;

the metallic blank includes a rigid base layer and a coating layerformed of a material that is deformable under the temperature andpressure conditions;

the coating layer is obtained by plasma spraying of one or more metallicpowders onto the rigid base layer;

the metallic layer is applied to the surface of the mold by plasmaspraying of one or more metallic powders;

the metallic layer includes one or more metallic materials selected fromthe group of aluminum, aluminum alloy, magnesium, magnesium alloy,copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy andaluminides, in particular titanium aluminide and nickel aluminide;

the reflector is polished;

a further coating is applied to the reflective layer;

the further coating is preferably of gold, applied by vacuum depositionor chemically; and

an oxidation protection layer is deposited on the fibers on the oppositeside to the metallic layer.

The invention enables fabrication of a metallic matrix compositematerial reflector whose reflective layer, on completion ofconsolidation of the metallized fibers:

conforms to the specified shape (without subsequent machining, butpossibly with simple polishing); and

is metallurgically attached by diffusion welding to the remainder of thestructure (without gluing), enabling the use of materials withcoefficients of thermal expansion and Young's moduli substantiallydifferent from those of the composite.

To obtain the specified shape the proposed solution is to place on thepreviously machined and polished mold coated with a mold release agentof an appropriate known type a deformable (conformable . . . ) metalliclayer that can be diffusion welded to the remainder of the structureunder the conditions of consolidation of the metallized fibers. Thisdeformable metallic layer can be:

a plasma sprayed deposit of metallic powder applied directly to themold, the nature of the metal being such that it can be diffusion weldedto the remainder of the structure;

a metallic blank preformed conventionally to dimensions approximatingthe specified shape, the material of which is deformable plastically orsuperplastically and can be diffusion welded to the remainder of thestructure under the conditions of consolidation of the metallizedfibers; or

a plasma sprayed deposit of metallic powder on the external surface(that adapted to face the mold) of a metallic blank conventionallypreformed to dimensions approximating the specified shape, the materialof which cannot be deformed plastically under the conditions ofconsolidation of the metallized fibers; the sprayed metallic powder mustbe diffusion weldable to the metallic blank during consolidation;likewise the metallic blank and the metallic matrix must be diffusionweldable (in the present instance, the "plasma deposit+preformed blank"combination is placed on the mold, with the "plasma deposit" against themold).

The invention also resides in a reflector obtained by this method, thatis to say a reflector formed by a reflective metallic layer extendingover a metallic or intermetallic matrix composite support wherein themetallic or intermetallic matrices of the support and the reflectivelayer are intermingled.

According to other preferred features of the invention; some of whichmay be combinable with others:

the metallic or intermetallic materials of the support and thereflective layer are different and their concentrations varycontinuously in the direction from the support to the reflective layerand vice versa; alternatively, these metallic materials are identical;

the support is symmetrical about a median surface of symmetry;

the support includes superposed layers of fibers with differentorientations in adjacent layers;

the fibers are carbon fibers;

the metallic matrix is formed from one or more materials selected fromthe group of aluminum, aluminum alloy, magnesium, magnesium alloy,copper, copper alloy, titanium, titanium alloy and aluminides, inparticular titanium aluminide and nickel aluminide;

the reflective metallic layer is formed from one or more materialsselected from the group of aluminum, aluminum alloy, magnesium,magnesium alloy, copper, copper alloy, nickel, nickel alloy, titanium,titanium alloy and aluminides, in particular titanium aluminide andnickel aluminide;

the matrix has an oxidation protection layer on the side opposite themetallic layer.

Objects, features and advantages of the invention emerge from thefollowing description given by way of non-limiting example withreference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic transverse section of a stack of layersproduced during the production of a concave first reflector;

FIG. 2 is a diagrammatic transverse section of another stack of layersproduced during the manufacture of a plane second reflector;

FIG. 3 is a diagrammatic transverse section of a plane third reflector;

FIG. 4 is a diagrammatic transverse section of a plane fourth reflector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Each figure shows the production by diffusion welding of a reflectorhaving a metallic reflective surface extending over a metallic orintermetallic matrix composite support of large size but smallthickness, preferably long fibers, although this is not mandatory.

One skilled in the art knows that it is not necessarily possible todiffusion weld any given metal or alloy to any other given metal oralloy: some combinations even give rise to violent reactions undercertain conditions of temperature and pressure; consequently, anyincompatible metallic elements are separated by one or more intermediatemetallic elements each compatible with both adjoining metallic elements.Also, great care is exercised to avoid the creation of eutectics.

The manufacture of the reflector requires a mold whose geometry is thatrequired for the external surface of the reflective surface. Themetallic (aluminum, nickel, copper, etc.) elements to constitute thereflective surface are disposed on the mold previously coated with moldrelease agent; metallized fibers; and preferably long fibers with alength of several centimeters (or even several tens of centimeters) arethen disposed over the metallic elements to constitute the reflectivesurface; during one and the same diffusion welding operation (thepressure, temperature and time of which depend on the metals used) thevarious metallic elements are compacted and bonded together by diffusioninto each other and the remainder of the composite; on removal from themold the reflector as a whole has a surface polish dependent on that ofthe mold. If the polish of the reflective surface obtained isinsufficient, additional polishing can be carried out and conventionalsurface coatings (Cr, Au, etc.) can be applied; the thickness of theseconventional coatings (typically 300 Å) is very much less than that ofthe reflective surface. The metallic elements can be applied to thesurface of the mold by any appropriate known deposition technique suchas plasma thermal spraying, for example. In the case of plane surfacesor surfaces that can be developed, the metallic elements to constitutethe reflective surface can be applied in the form of a plasticallydeformable metallic film or strip placed on the mold previously coatedwith mold release agent. As previously, the film or tape is bonded bydiffusion welding to the constituents of the composite. After removalfrom the mold, if the polish of the reflective surface is insufficient,the external surface can be polished. As an alternative, the metallicelements can be applied by deposition onto a base metallic layer alsoformed of all or part of the metallic elements on a surface of the baselayer having at least approximately the geometrical shape required forthe reflective surface; this base layer is then placed on the surface ofthe mold, the coated surface facing the mold surface. The exactconformance to the required geometry of the reflective surface obtainedin this way then results, as in the previously mentioned case of film orstrips, from plastic deformation of the coating, or even of the baselayer, under conditions of temperature and pressure enablingconsolidation/diffusion welding so as to mate intimately with thesurface of the mold.

It is important to note that, according to the invention, the reflectivesurface is formed at the same time as its support, to which it isintimately bonded (there is interdiffusion of atoms and thereforemetallurgical continuity in the direction of the thickness of thereflector).

A typical example of the manufacture of a mirror according to thepresent invention is given below:

1. polishing of the external surface of the mold;

2. coating of the mold with a mold release agent;

3. deposition onto the coated mold of the metallic elements of thereflective surface (as just mentioned, there are other methods thandeposition for applying the metallic elements);

4. draping onto the mold, covered with the metallic elements, ofmetallized "pre-impregnated members", this draping being preferably suchthat there is a central surface of symmetry of the composite (thissurface, even if the required reflector is convex, concave or acombination of the two, is at least locally an approximately planesurface, all the more so in that the radius of curvature of thereflector is in practice very much greater than its thickness);

5. application of the hot consolidation cycle to the draped formresulting from operation 4: maximal temperature typically between 400°C. and 650° C., pressure typically between 5 MPa and 300 MPa, durationbetween 15 minutes and 3 hours for light alloy matrices; forintermetallic matrices the parameters are more like 900° C. to 1200° C.at a pressure of 200 MPa for 30 minutes to one hour (the actual valuesto be used depend on the consolidated matrix and the metallic elementsused);

6. removal from the mold and cleaning of the reflective surface; and

7. where applicable: additional polishing and further coating.

The metallized "pre-impregnated members" mentioned above can be ofvarious sorts, their main property being that they are diffusion welded:

metallized carbon fibers, produced for example by metallizing carbonfilaments by vapor phase physical deposition;

stranded carbon fibers metallized by dipping into the molten alloy; and

1D, 2D or 3D plates of carbon fibers metallized by infiltration of themolten alloy.

With reference to the matrices, in theory any metal can be used in thepresent invention. Nevertheless, and given their density in particular,aluminum, aluminum alloy, magnesium and magnesium alloy are obviouslypreferable matrices for aerospace applications. Likewise, if the abilityto withstand temperatures above 400° C. is required, a copper or copperalloy matrix can be advantageous, given its good thermal conductivity.If there is a requirement to withstand temperatures of 800° C. to 1000°C., nickel and/or titanium aluminide matrices are preferable.

With reference to the fibers, they are preferably carbon fibers; themost advantageous are those having a very high modulus, a very hightensile strength and the most negative possible coefficient of thermalexpansion combined with a high thermal conductivity. Fibers based onpitch, for example TONEN FT 700 fibers, are particularly advantageous;the specifications of FT 700 fibers are as follows:

    ______________________________________                                        density               2.16 g/cm.sup.3                                         tensile strength      3 300 MPa                                               Young's modulus       700 GPa                                                 diameter              10 μM                                                number of filaments per wick                                                                        3 000 (3 K)                                             coefficient of thermal                                                                              -1.5 10.sup.-6 K.sup.-1                                 expansion α.sub.L                                                       ______________________________________                                    

As an alternative, the fibers are silicon carbide or alumina fibers.

EXAMPLES

a) First example (see FIG. 1)

A9 type aluminum powder (99.9% pure) was deposited by plasma sprayingonto a polished molybdenum convex mold 1 coated with boron nitride (moldrelease agent 2). Onto this 120 μm thick deposit 3 were drapedquasi-isotropically (0°, +45°, +90°, -45°, -45°, +90°, +45°, 0°) layers4 through 7 and 7' through 4' of FT 700 carbon fibers with a very highYoung's modulus previously metallized by vapor phase physical depositionof pure (A5) aluminum (the vapor phase physical deposition process beingdirectional, the FT 700 wicks were first spread by blowing with air, inpractice transversely (hairdryer type)) to facilitate the metallizationof each filament; a 100 μm thick pure (A5) aluminum film 8 was thenapplied. The resulting assembly was consolidated at raised temperature(595° C.) and under pressure (25 MPa) with the maximum pressure andtemperature maintained for 25 minutes, and in a vacuum of 10⁻² Torr. Thecomposite was produced by diffusion welding and the layer 3 was integralwith it. The aluminum matrix composite material mirror 10 removed fromthe mold had an aluminum surface coating with a polish dependent on thatof the molybdenum mold (if the polish is insufficient the surface can bepolished).

The number of layers of fibers is in practice very much greater than theeight layers shown in FIG. 1 as their unit thickness is in the order often microns and the thickness required for the support is typically inthe order of a few millimeters.

The advantage of the aluminum layer 8 of similar thickness to the activelayer 3 is that it provides protection and guarantees symmetry relativeto its median plane, the advantage of which is that it avoidsdeformation on cooling after consolidation.

Note that the quasi-isotropic draping involves changing the orientationof the layers of fibers by 45° between layers; the stacking of thelayers produces a median surface of symmetry S to either side of whichthe layers are oriented symmetrically: the advantage of this is that itavoids deformation on cooling.

The following specifications were obtained with a quasi-isotropic planeplate 200 mm×200 mm×2.8 mm with a fiber ratio (the mass ratio of barefibers to the same fibers after metallization) of 50% carried out underthe same conditions:

    ______________________________________                                        Young's modulus E     133 GPa                                                 coefficient of thermal expansion α.sub.L                                                      2.65 × 10.sup.-6 ° C..sup.-1               transverse thermal conductivity K.sub.T                                                             152 W.m.sup.-1 ° C..sup.-1                       density ρ         2.4 g/cm.sup.3                                          ______________________________________                                    

b) Second example (see FIG. 2)

A 120 μm thick superplastic 7475 aluminum film 13 was placed on arefractory stainless steel mold 11 coated with boron nitride moldrelease agent 12 so that it adopted approximately the final requiredshape. Layers 14 through 17 and 17' through 14' of FT 700 carbon fiberswith a very high Young's modulus metallized with A5 aluminum were drapedquasi-isotropically on this film. A 100 μm thick A5 aluminum film 18 wasplaced on this draped subassembly. The resulting assembly wasconsolidated as in the first example. After diffusion welding of theassembly the part was removed from the mold and the superplasticaluminum active surface 13 had deformed to assume the exact shape of themold, producing a mirror 20 having a central plane of symmetry S. Amirror made in this manner can be given a final polish and an additional300 Å coating of gold can be deposited in vacuum or chemically.

The specifications obtained were similar to those of the first example.

c) Third example (see FIG. 3)

A9 aluminum powder was plasma sprayed onto a polished molybdenum planemold 21 coated with boron nitride mold release agent 22. A 10 μm thickfilm of T 40 titanium 23A was placed on the resulting 100 μm thickdeposit 23. Layers 24 through 27 and 27' through 24' of FT 700 carbonfibers having a very high Young's modulus metallized with GA6Z1magnesium alloy by vapor phase physical deposition were drapedquasi-isotropically onto this film 23A. A film 28 of the same kind asthe layer 23A, i.e. a 10 μm thick film of T 40 titanium, was placed onthis draped subassembly. The resulting assembly was consolidated asfollows:

    ______________________________________                                        maximal temperature  490°                                                                          C.                                                pressure             25     MPa                                               vacuum               10.sup.-2                                                                            Torr                                              duration             30     minutes                                           ______________________________________                                    

The composite was formed by diffusion welding in which the layer 23 andthe layer 23A interpenetrate and the layer 23A and the compositeinterpenetrate. After removal from the mold the magnesium matrixcomposite material mirror 30 had an aluminum surface coating with apolish dependent on that of the molybdenum mold. The titanium layer 23Aserved as a barrier between the aluminum and the magnesium which,otherwise in contact, would have formed a eutectic. The titanium film 28protected the magnesium from oxidation.

The following specifications were obtained with a quasi-isotropic planeplate 200 mm×200 mm×2.8 mm with a fiber ratio of 50%:

    ______________________________________                                        E                127 GPa                                                      α.sub.L    2.10 × 10.sup.-6 ° C..sup.-1                    K.sub.T          88 W.m.sup.-1 ° C..sup.-1                             ρ            2 g/cm.sup.3                                                 ______________________________________                                    

As an alternative the deposit 23 can be applied to the film 23A beforeit is placed in contact with the surface of the mold.

d) Fourth example (see FIG. 4)

A 100 μm thick superplastic 7475 aluminum film 33 and then a 10 μm thickfilm 33A of pure (T 40) titanium were placed on a refractory stainlesssteel mold 31 coated with boron nitride mold release agent 32. Eightunidirectional plates 34 through 37 and 37' through 34' 0.5 mm thickwith a single fiber alignment direction formed from FT 700 carbon fibersmetallized by low pressure infiltration of AZ 61 magnesium into thecarbon wicks were then stacked; these plates were placed so that thefibers constituted a quasi-isotropic reinforcement. Onto this stack wereplaced a 10 μm thick film 38A of T 40 titanium and then a 100 μm thickfilm 38 of superplastic 7475 aluminum. This combination was consolidatedas in example c). After removal from the mold the aluminum activesurface (that towards the mold) had assumed the shape of the moldsurface, yielding a mirror 40 having a central plane of symmetry S.

The specifications obtained were of the same order of magnitude as thosefor example c).

e) Fifth example (no diagram)

For mirrors requiring high stiffness, the mirrors described above can beused as bases for sandwich constructions using an aluminum honeycombcore, for example, the bases being bonded to the core using thermallyconductive glue or, preferably, by low-temperature brazing, the type ofbrazing depending on the nature of the elements to be assembled.

The various examples given above have the common feature of eachcorresponding to a mirror of great dimensional stability embodyingcarbon fibers in a metallic or intermetallic matrix (aluminum, aluminumalloy, magnesium, magnesium alloy, copper or copper alloy). The mirroris constructed by diffusion welding layers of metallized carbon fibers,stranded metallized carbon fibers or plates of pre-impregnated carbonfibers with a central plane of symmetry and the reflective metalliccoating is integrated with the support by diffusion welding duringconsolidation of the composite, diffusion towards the mold beinginhibited by a mold release agent. Thus a single operation produces amirror having a metallic reflective surface whose polish depends on thatof the mold and whose dimensional stability properties are excellent:modulus, strength, coefficient of thermal expansion, transverse thermalconductivity, absence of moisture absorption. If required, the externalcoating can be polished, after removal from the mold, and receivefurther conventional coatings (Cr, Au, etc).

The above description is obviously given by way of non-limiting exampleonly and numerous variants can be put forward by one skilled in the artwithout departing from the scope of the invention.

There is claimed:
 1. A method of manufacturing a reflector formed by areflective metallic layer on a metallic matrix composite support, saidmethod comprising the steps of:selecting a metallic layer having areflective surface whose shape is at least substantially conforming to arequired geometrical shape of said reflector, said metallic layer beingdisposed on a mold surface having a geometrical shape complementary tosaid required geometrical shape; placing fibers adapted to constitutesaid composite support on said metallic layer, said fibers constitutinga fiber layer having a first side and an opposing second side, saidfiber layer being metallized by a metallic or intermetallic materialadapted to form said metallic matrix; and subjecting said metallic layerand said metallized fibers to temperature and pressure conditionsadapted to press said reflective surface strongly against said moldsurface and to cause diffusion welding of said metallic layer with saidfirst side of said fiber layer of said metallized fibers and of saidmetallized fibers with themselves within said fiber layer so as tointegrate said metallic layer to said composite support duringconsolidation of said composite support.
 2. A manufacturing methodaccording to claim 1 further comprising the step of selecting carbonfibers as said fibers.
 3. A manufacturing method according to claim 1further comprising the step of symmetrically disposing said fibers oneither side of a median surface of symmetry.
 4. A manufacturing methodaccording to claim 1 further comprising the step of placing said fibersin a random free state.
 5. A manufacturing method according to claim 4further comprising the step of dividing said fibers into an equal numberof layers disposed symmetrically to either side of a median surface ofsymmetry.
 6. A manufacturing method according to claim 1 furthercomprising the step of preparing said metallized fibers by vapor phasephysical deposition of a layer of metallization onto said fibers so thatsaid metallized fibers are flexible.
 7. A manufacturing method accordingto claim 1 further comprising the step of selecting stranded fibers assaid fibers.
 8. A manufacturing method according to claim 7 furthercomprising the step of metallizing said stranded fibers by dipping saidstranded fibers into a bath of molten metallic material.
 9. Amanufacturing method according to claim 1 further comprising the step ofgrouping said fibers in plates wherein said fibers have one, two orthree alignment directions.
 10. A manufacturing method according toclaim 9 further comprising the step of metallizing said plates of fibershaving one, two or three alignment directions by infiltration of saidmetallic material in a molten state under pressure.
 11. A manufacturingmethod according to claim 1 including the step of selecting saidmetallized metallic and intermetallic material from a group consistingof aluminum, aluminum alloy, magnesium, magnesium alloy, copper, copperalloy, titanium, titanium alloy and aluminides, in particular titaniumaluminide and nickel aluminide.
 12. A manufacturing method according toclaim 1 further comprising the step of placing said metallic layer onsaid mold surface in the form of one or more deformable films.
 13. Amanufacturing method according to claim 1 further comprising the step ofobtaining said metallic layer by preparation of a metallic blank havinga blank surface area at least approximately identical to the requiredgeometrical shape, said metallic blank being deformable under saidtemperature and pressure conditions at least in the direction of thethickness of said metallic blank.
 14. A manufacturing method accordingto claim 13 further comprising the step of selecting said metallic blanksuch that said metallic blank is deformable under said temperature andpressure conditions throughout said thickness.
 15. A manufacturingmethod according to claim 13 further comprising the step of selectingsaid metallic blank to include a rigid base layer and a coating layerformed from a material that is deformable under said temperature andpressure conditions.
 16. A manufacturing method according to claim 15further comprising the step of plasma spraying one or more metallicpowders onto said rigid base layer to form said coating layer.
 17. Amanufacturing method according to claim 1 further comprising the step ofapplying said metallic layer to said mold surface by plasma spraying ofone or more metallic powders.
 18. A manufacturing method according toclaim 1 further comprising the step of selecting one or more metallicmaterials from a group consisting of aluminum, aluminum alloy,magnesium, magnesium alloy, copper, copper alloy, nickel, nickel alloy,titanium, titanium alloy and aluminides, in particular titaniumaluminide and nickel aluminide to form said metallic layer.
 19. Amanufacturing method according to claim 1 further comprising the step ofpolishing said reflector.
 20. A manufacturing method according to claim1 further comprising the step of applying a coating to said reflectivemetallic layer.
 21. A manufacturing method according to claim 20 whereinsaid coating applied in said applying step is gold.
 22. A manufacturingmethod according to claim 1 further comprising the step of depositing anoxidation protection layer on said second side of said fiber layer.